to send multiple values with check boxes, you need to make sure the name of the check box ends in "[]"
fro example:<input type="checkbox" name="Services[]" value="Drop-In Visits" id="Services_1" />
this creates an array to hold all of the cehcked values, to output the array in the email, you will need to use the implode function:
<?php echo((isset($_POST["Services"]))?implode(", ", $_POST["Services"]):"") ?>